S42 Turbocharger

The JM Turbo Coopers S42 is an upgraded, high-pressure, high-flow dual-scrolling turbocharger engineered to replace the factory K03 unit on MINI Cooper S and John Cooper Works models with N14 and N18 engines. This turbo utilizes a 42mm compressor, larger than the stock JWC turbo, to deliver boost that begins earlier and lasts longer, providing outstanding response and significant torque and power gains across the entire powerband. The 42mm design specifically enhances top-end power. Constructed with a lightened, high-flow exhaust turbine and high-strength K04 internals, the S42 is designed for higher pressure applications. It incorporates an upgraded 360-degree bearing for improved reliability and a water-cooled bearing housing for optimal temperature management. The turbine housing is made from a high-temperature alloy and features a dual-scrolling design. Installation requires a tune to achieve optimal power gains; running without a tune will result in minimal horsepower increases. Estimated gains are approximately 60hp with supporting modifications like a tune, intercooler, downpipe, and cold air intake. Further gains of 100hp+ are achievable with additional upgrades such as a ported head, larger valves, and a larger exhaust system. It is recommended to ensure a clean or new aftermarket catalytic converter and intercooler to prevent boost codes. The OEM intake boot may require modification for installation: the inner sleeve needs removal for N14 engines, and for N18 engines, the boot at the turbo connection might need to be gently expanded with a heat gun. Aftermarket intakes like AEM, NM Engineering, and Forge may also require the boot hose to be warmed and stretched. This turbocharger is not for sale or use in the state of California on any pollution-controlled vehicle, as per the California Air Resources Board.